1. Field of the Invention
The present invention relates generally to exhaust systems for internal combustion engines. More specifically, the present invention relates to inserts for engine exhaust systems for reducing or otherwise baffling or modifying the sound of the exhaust when the engine is in operation. The inserts may also serve as spark arrestors as well.
2. Description of the Related Art
While virtually all automobiles and trucks come equipped at the time of purchase with adequate sound suppression systems for their engines, this is not necessarily the case with many vehicles intended for off-road use. Personal watercraft and various racing and competition vehicles, wheeled or otherwise, may have relatively loud engine exhaust systems in order to reduce restrictive back pressure in the exhaust. In other cases, vehicle owners have modified the exhaust systems of their automobiles, motorcycles, etc. in an attempt to provide a distinctive sound, or perhaps a distinctive appearance for the exhaust system where it is exposed, as is the case with motorcycles.
Perhaps the easiest way of reducing the back pressure in an exhaust system is to construct a system wherein all of the pipes are completely open, i.e., without internal restriction. Many motorcycle owners and operators have attempted operation with such open exhaust systems, and in fact, the sound output of such systems may be legal and/or acceptable in some conditions, particularly with smaller engines and where the type of vehicle is not heavily regulated insofar as its exhaust emissions (sound and otherwise) are concerned.
While this may be acceptable in some circumstances, the resulting noise level is certainly not acceptable in most operating environments. One problem with such modification is that the resulting modified exhaust system may produce a sound level that exceeds the maximum permitted by law for the jurisdiction and/or type of vehicle. This may be true of racing, competition, and off road vehicles as well, depending upon the environment of use, rules of the sanctioning body, and perhaps other factors. When this occurs, the owner or operator of the vehicle must find some way to reduce the sound output of the exhaust system.
Various techniques have been developed in the past for reducing the sound level output of an internal combustion engine exhaust system, e.g., stuffing steel wool and/or glass fiber packing into the pipe or tube, etc. Such a modification is easily accomplished, but the resulting back pressure in the system is likely excessive. Other than the above well-known technique, the present inventor is only aware of exhaust systems and components (replacement mufflers, etc.) that incorporate rigid internal baffling installed at the time of manufacture. The end user cannot easily modify such an exhaust system by removing and/or replacing one or more inserts therein to affect the sound output of the exhaust system.
An example of such a manufactured exhaust system is disclosed in Japanese Patent No. 6-323,136 published on Nov. 22, 1994. This reference describes (according to the drawings and English abstract) an internal supporting structure for a concentrically installed rigid tube and catalytic converter assembly within an outer exhaust pipe. The assembly is permanently installed within the outer pipe at the time of manufacture of the device, with no means provided for inserting the internal assembly within an existing pipe having a closed wall, particularly in the case of a curved pipe.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed. Thus, inserts for engine exhaust systems solving the aforementioned problems is desired.